This invention relates to bistable logical elements and specifically to bistable multivibrators generally known as flip-flops.
A flip-flop is a bistable electronic circuit which stores a selected logical state in response to a clock pulse and one or more data input signals. Most flip-flops are designed to store the logical state represented by an input signal present when a leading edge of a clock pulse is received. Conventionally, the leading edge of a clock pulse is that portion of the clock pulse waveform which changes from a low level to a high level. A typical flip-flop using metal oxide semiconductor (MOS) technology is shown in Holt, Electronic Circuits Digital and Analog, page 265 (1978), which is hereby incorporated by reference. Other prior art flip-flops store the logical state indicated by an input signal on receipt of the trailing edge of a clock pulse. The trailing edge of a clock pulse is that time when the clock pulse changes from a high level to a low level. An example of a flip-flop capable of changing its logical state on the trailing edge of a clock signal is shown Hepworth, et al., U.S. Pat. No. 3,976,949, "Edge Sensitive Set-Preset Flip-flop", issued Aug. 24, 1976. Flip-flops which store data either on the leading edge or the trailing edge of the clock signal are limited in that they can only store one logical state per clock pulse. Therefore, it is desirable to provide a flip-flop which stores logical information at a rate faster than once per clock pulse.